Integrative Analyses Reveal the Physiological and Molecular Role of Prohexadione Calcium in Regulating Salt Tolerance in Rice
Rui Deng, Li Yao, Naijie Feng, Dianfeng Zheng, Youwei Du, Aaqil Khan, Yingbin Xue, Jianqin Zhang, Yanan Feng
Abstract
Salinity stress severely restricts rice growth. Prohexadione calcium (Pro-Ca) modulation can effectively alleviate salt stress in rice. In this study, we explored the effects of Pro-Ca on enhancing salt tolerance in two rice varieties, IR29 and HD96-1. The results revealed that Pro-Ca markedly enhanced root and shoot morphological traits and improved plant biomass under salt stress. Chlorophyll a and b content were significantly increased, which improved photosynthetic capacity. Transcriptomic and metabolomic data showed that Pro-Ca significantly up-regulated the expression of genes involved in E3 ubiquitin ligases in IR29 and HD96-1 by 2.5-fold and 3-fold, respectively, thereby maintaining Na+ and K+ homeostasis by reducing Na+. Moreover, Pro-Ca treatment significantly down-regulated the expression of Lhcb1, Lhcb2, Lhcb3, Lhcb5, and Lhcb6 in IR29 under salt stress, which led to an increase in photosynthetic efficiency. Furthermore, salt stress + Pro-Ca significantly increased the A-AAR of IR29 and HD96-1 by 2.9-fold and 2.5-fold, respectively, and inhibited endogenous cytokinin synthesis and signal transduction, which promoted root growth. The current findings suggested that Pro-Ca effectively alleviated the harmful effects of salt stress on rice by maintaining abscisic acid content and by promoting oxylipin synthesis. This study provides a molecular basis for Pro-Ca to alleviate salt stress in rice.